1. Field of the Invention
This invention relates generally to the field of intraocular lenses after cataract extraction and in particular to intraocular lenses that reduce secondary opacification of the lens capsules.
2. Description of Prior Art
The insertion of an artificial intraocular lens in the human eye is a well-known surgical procedure to cure cataract, a common eye disorder in which the natural lens becomes gradually less transparent.
Typically in such a procedure, the opaque lens material is removed from the lens bag, and is replaced by an artificial intraocular lens with the same optical properties. Several lens types have been designed since the original idea of Ridley in 1949. These types include e.g. anterior chamber angle supported lenses, iris supported lenses, posterior chamber sulcus fixated lenses, and in-the-bag lenses. None of these lenses have the property of preventing the secondary opacification of the posterior capsule of the lens bag. This secondary opacification is due to a proliferation of the remaining epithelial cells in the lens bag. Ultimately, after a variable time interval, secondary opacification occurs in up to eighty percent of the operated eyes. Many remedies, largely unsuccessful, have been advocated to prevent this major cause of visual loss after cataract surgery. These include the introduction of chemical substances with the intraocular lens [salts, U.S. Pat. No. 5,370,687 to Poler; taxol, U.S. Pat. No. 5,576,345 to Mangnasson], the physical removal of remaining proliferative cells within the lens bag [use of probe, U.S. Pat. No. 5,445,636 to Bretton], and special lens designs that include metal coatings [U.S. Pat. No. 5,593,438 to Akhavi], adhesive coatings [U.S. Pat. No. 5,002,571 to O'Donnell], roughened surfaces on the lens [U.S. Pat. Nos. 5,405,385 to Heimke, 4,808,181 to Kelman, 5,549,670 to Young], or mechanical with multiple fixation rings attached to the intraocular lens [U.S. Pat. No. 5,366,501 to Langerman]. The only efficient cure for an established secondary opacification of the posterior capsule at present is the surgically induced rupture of the opaque posterior capsule, or capsulotomy, with a capsulotomy needle or with a Nd-YAG Q switched laser. A specially designed intraocular lens can be helpful in aforementioned surgical procedures [U.S. Pat. No. 4,485,499 and 4,547,915 to Castleman]. These secondary capsulotomies however increase the complication rate after cataract surgery to the level of the older, now mostly abandoned intracapsular technique of cataract extraction. Complications e.g. include retinal detachment, glaucoma, cystoid macular edema and pitting of the intraocular lens.
All the intraocular lenses mentioned in prior art have a common feature. They are all placed in the lens bag and they do not prevent the proliferation of the remaining capsular epithelial cells behind the optical pat of the intraocular lens with opacification as a result. Even the surgical removal of the central pat of the posterior capsule immediately before implantation does not prevent further cellular proliferation. I have demonstrated recently that these cells do not need the support of the capsule to further proliferate and to reclose the opening of the posterior curvilinear continuous capsulorhexis (PCCC).